Weightpaint fix.
Weight painting was recoded in 2.40 to support all features from vertex
paint. That code uses a 'soft' brush by default, which makes it impossible
to assign exact weight values on a single click (which used to be possible)
I've made that an option now, so you can disable it for single-click setting
of values on vertices within the brush (if 'use vertex distances' is
set, of course).
d90b676bbb